The present invention relates to a magnetic head slider and a magnetic disk drive carrying the magnetic head slider thereon. More particularly, the present invention is concerned with the shape of an air bearing surface of a magnetic head slider.
A magnetic head slider, which is adapted to fly over a rotating disk recording medium while maintaining a slight spacing (flying height) with respect to the disk, is used in a magnetic disk drive. Usually, the magnetic head slider is provided at a trailing edge of a slider with a magnetic transducer for write and read of information to and from a disk recording medium. In order to enhance the memory capacity, it is required for a magnetic disk drive to further increase the bit (recording in the circumferential direction) density and track (recording in the radial direction) density. In particular, as one technique for increasing the bit density, it is required to cause a slider to fly in a low flying height as close as possible to the disk recording medium.
At present, one of the effective methods for satisfying such a strict requirement for a low flying height is to use a magnetic head slider provided with a mechanism for controlling the flying height of a magnetic transducer and the vicinity thereof, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. Hei 5-20635). In this method, when the magnetic transducer of the magnetic head slider reads information stored on a disk recording medium, the magnetic transducer is heated with a heater or the like formed in the vicinity thereof and is approximated toward the disk recording medium by utilizing the resulting heat deformation. On the other hand, when writing information onto the disk recording medium, the magnetic transducer approaches the disk temporarily by utilizing a spontaneous heat deformation caused by an electric current flowing in the magnetic transducer. According to this method, the magnetic transducer can be approximated temporarily to the disk recording medium only at the time of writing or reading information to or from the disk recording medium. When the magnetic transducer does not perform an information write or read operation, the flying height can be set relatively high. Therefore, variations in flying height attributable to the manufacturing process of the magnetic head slider and the magnetic disk drive and changes in flying height caused by changes in pressure and temperature can be tolerated in wide ranges. Consequently, both a low flying height for improving the magnetic recording capacity and the improvement in reliability of the magnetic disk drive can be attained at the same time.
In Patent Document 2 (Japanese Patent Laid-Open No.2001-297421) is disclosed a technique of making the flying height almost uniform throughout the whole surface of a magnetic disk and decreasing a change in flying height in a high land. This technique is characterized in that there are disposed a rail surface including a magnetic transducer and a rail surface at a front position on a leading side of the rail surface through a groove surface. Also proposed is a shape of an air bearing surface wherein the rail surface subsequent to the leading side is once constricted in width at a position just before the magnetic transducer.
In the magnetic head slider having a flying height control mechanism in the vicinity of the magnetic transducer, which is described in Patent Document 1, however, when the flying height control mechanism is operated, the air bearing surface located near the magnetic transducer is projected and deformed out of plane, causing a change in the state of generation of a flying force on the air bearing surface. The change in the flying force caused by a deformation in the direction in which the projection of the air bearing surface increases acts in a direction to increase the flying height near the magnetic transducer. The amount of this increase of the flying height with an increase of the flying force offsets the amount of decrease of the flying height caused by the projection. Therefore, a larger control power is needed if an attempt is made to obtain a desired decrease of the flying height. Such an increase of the control power is not desirable for the magnetic disk drive for which the operation at a low power consumption is required more and more strongly. Further, a smaller magnetic head slider used in a small-sized magnetic disk drive has a tendency that an area ratio of the projectingly deformed region on the air bearing surface increases and so increases the offset ratio in flying height caused by deformation.
Therefore, a lower power consumption of the flying height control mechanism is required in order to attain a lower power consumption of the magnetic disk drive. For the air bearing surface of the slider it is required to provide a slider structure able to lower the offset ratio of flying height caused by projecting deformation and afford a change in flying height caused by a low control power.
According to the technique described in Patent Document 2, it is possible to decrease somewhat the offset ratio of flying height. However, the portion which generates the highest pressure on the air bearing surface lies on the rail surface including the magnetic transducer and there occurs a change in flying force caused by projecting deformation, not attaining a fundamental air bearing surface structure able to decrease greatly the offset ratio of flying height. Further, since the generated pressure is offset to the center of the slider as a whole, there exists a situation where an increase of variations in flying height attributable to the longitudinal shape of the air bearing surface, i.e., crown, or to a lowering of pitch rigidity must be suppressed.